Water flowing through channels such as drainage ditches and streams can become contaminated with silt—fine particles of sediment and organic material—from many sources. This is especially true when the channels are located in places of environmental disturbance, such as along roadways, near construction sites, and in agricultural areas. Such disturbances expose soil to erosion and remove the natural vegetation which tends to slow down water flow. Silt can be harmful to aquatic life, and also tends to accumulate in ways that result in restrictions in the flow of water. This can lead to flooding, and in extreme cases, to roadway washouts or even landslides.
Parties responsible for the maintenance of environmental quality, as well as the safety of rural roads, face a dilemma: permitting the rapid flow of silt-laden water is preferable to avoid damming of water channels and the associated flooding, but on the other hand, healthy fisheries require clean water. Water channel design which limits the transport of silt tends to involve damming, using hay bales, silt fences, and similar structures. These dams slow water flow to permit settling, but results in large deposits of silt which must be laboriously removed from behind the dam. Additionally, dams are problematic during periods of unusually high water flow. At such times it may be preferable to permit a high rate of flow to prevent flooding, while making silt removal a lesser priority. Simple dams cannot accommodate this need, and instead lead to flooding if the dam is sturdy, or to dam failure if it is not, which releases the built up silt.
What is needed, then, is a means of promoting the settling of silt without unduly restricting water flow, and permitting the collected silt to be easily removed to restore the system to full operation.